1. Field of the Invention
The present invention relates to a harmonic current attenuating device of a motor, and more particularly to a harmonic current attenuating device of a motor which can attenuate the harmonic current generated while driving a motor of a cleaner.
2. Discussion of Related Art
A typical motor driving circuit in a cleaner is shown in FIG. 1. As can be seen from FIG. 1, a motor 30 is driven by an alternating current power with a commercial frequency supplied from a power supplying unit 10, the internal air is compulsorily circulated by an impeller which is rotated by the engagement with the motor, and then contaminants like dusts are sucked in from a suction opening by the wind generated by the pressure difference between an exterior and an interior of the cleaner.
FIG. 2 shows waveforms of the voltage V and current I supplied to the motor 30.
In the meanwhile, the harmonic current is generated because the sine wave voltage supplied from the power supplying unit 10 is phase-controlled and changed to a non-sinusoidal wave voltage by a TRIAC (Triode AC switch) 40 which is switching-controlled by a gate signal, and then is supplied to the motor 30.
With the spread of these goods, the total amount of the harmonic current drawn to a power system is increased, causing an operating disorder of a power condenser and of a brake and the breakdown of a transformer.
In order to prevent the disorder due to the harmonic current as described above, an IEC (International Electrotechnical Commission) established a standard of limiting the harmonic current. According to this standard, among various harmonic currents generated at the cleaner when controlling at the phase of 90.degree., the one that matters is a 3rd harmonic current.
Thus, researches have been made on the technique for attenuating the 3rd harmonic current in various technical fields related to the cleaner.